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You can highlight a section of a trace by making the points alternately too high and too low by a
suitable amount. Providing the memory length is not too short, the compaction algorithm will give
the effect of a thicker trace.
The lengths of the output trace and the input trace need not be the same. You can even make the
output trace longer than the input trace, but you will need to unzoom it to see it all. This feature
can be used to avoid compaction problems with non-linear horizontal scales. It can also be used
to show several versions of a function at the same time, without having to set up a separate script
for each one.
If your program structure is complicated, consider typing all the IFs, ELSEIFs, ENDIFs, FORs,
NEXTs, etc and then clicking Apply. You wont get any output, but the system will tell you if the
structure is acceptable. Then you can insert the actual program statements.
Always try to make the script as independent as possible of variables such as V/Div, T/Div, and
memory length, unless that would make it harder to understand. If so, give some values as
examples, and explain how the script would have to change if the variables changed.
Errors
The instrument VBS tries hard to help you when errors occur.
Errors may be of two main types:
•
The script may not be usable because the interpreter cannot construct a logical structure
from it.
•
The script may be usable, but may fail while running because an incomputable function has
been requested.
Sometimes the line number given for an error is wrong. This can happen when the error is of this
general type:
Missing "Next" Missing "End If"
Extra "Next" Missing "Until" etc.
This happens because VBS cannot know where you should have put the statement.
If at some point during the calculation of an output array, a value goes outside the allowed range,
the calculation will stop, and you will see the new values up to the point of the stoppage. To the
right of that point, the trace will display the previous values. In fact, if you deliberately recalculate
only a part of a trace, you can have a mixture of new and old values.
The following figure shows an error message type seen if a calculation has tried to set a value
outside the range -32768 to +32767. It takes extra time to guard against this. However, unless
you are sure that it will not happen, some kind of check is needed.
264
SDA-OM-E Rev H
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